Parents need to know that this Star Trek series is by far the most violent entry in the franchise. One alien race was enslaved and forced into concentration camps, while another has been genetically engineered to become the perfect fighting machine (their masters take over a portion of the galaxy and prove to be brutal dictators). A secret faction within the Federation engages in biological warfare. Later seasons focus on an all-out war against the Dominon, which costs billions of lives and features several battle scenes involving hundreds of starships.